The present invention relates to printing graphics, such as alphanumeric symbols, designs, logos and other artwork, on fabric. More particularly, the present invention relates to printing graphics on fabric using a thermal transfer printer.
Typically, graphics are printed on fabric using a thermal transfer process. In such a process a thermal transfer ribbon, including a colorant layer of pigment dispersed in a wax, resin or wax-resin vehicle, is used to print the desired graphic onto a thermally stable substrate, such as thermal paper, coated with a resin binder. The printed paper is then placed print side down on the fabric, and the colorant is transferred to the fabric in a press by the application of heat and pressure. The resin binder is also transferred, and the resin binds the colorant to the fabric.
Generally, the printed graphic is defined by one or more print areas covered by the colorant and adjacent "white" or non-print areas. However, since the entire surface of the thermal paper is coated with the binder, binder transfers to the fabric throughout this adjacent, non-print area, as well as in the areas covered by the colorant. The binder gives the non-print areas of the fabric an undesirable hand or texture and also seals the fabric weave together, which prevents the free passage air and moisture through the fabric in the non-print areas. Further, the resin binder is not transparent and leaves a shadow around the graphic. The resin shadow is particularly noticeable on colors other than white. Thus, the above-described method of printing is generally limited to use with white fabrics.
According to an alternative process, typically used in most high volume applications, the thermal transfer is prepared by screen printing or lithographically printing a desired graphic onto a thermally stable substrate. Since both processes employ inks instead of the pigmented wax or resin compounds described above in connection with thermal transfer ribbons, the resin binder and its associated disadvantages are eliminated. However, screen printing and lithographic printing, are labor intensive processes requiring artwork, ink mixing, color separation, printing screens or color separation films, a UV exposure step, and the use of emulsions, developers and other chemicals in addition to the inks. Moreover, the prepared screens or films can be use to print single size designs only.
It is, therefore, an object of the invention to provide a method for printing graphics on fabric which requires less labor and equipment than screen printing or lithographic printing and which does not require the inks and other chemicals used in these processes.
It is a further object of the invention to provide a method wherein the graphic is printed using a thermal printer and the final product is coated with binder in only those areas corresponding to the print area of the graphic.
It is yet another object of the invention to provide an apparatus for carrying out such a process.